Today's artillery shells are equipped with a safety and arming (“S&A”) device that permits detonation of the carried explosive only after the projectile has experienced a valid progression of physical launch conditions, including a huge initial acceleration. The arming device functions with sequential interlocks to remove a barrier in the fire train, to move out-of-line fire-train components into alignment or to close or open a switch. Once armed, the device can be fused with, e.g., an electrical discharge or a laser pulse. For safety, the S&A is required to be able to withstand a munitions mishandling drop from 40 ft. without damage or arming.
A typical arming device is centimeter-sized and piece-part assembled using screws, pins, springs and tight-tolerance machined components. Shelf life is affected by the use of dissimilar materials and by the need for lubrication. Recent arming device modernizing efforts have been motivated by lower cost, weight and volume. One such arrangement, described by Robinson in U.S. Pat. No. 6,167,809, entitled “Ultra-Miniature, Monolithic, Mechanical Safety-and-Arming Device for Projected Munitions,” is directed to a monolithic metal (nickel) device fabricated using the well-known LIGA (an acronym from German words for lithography, electroplating and molding) micro machining process.
Most conventional miniature S&A devices respond only to a single environmental condition, namely the initial acceleration at launch. Accordingly, what is needed in the art is an improved device that responds to more than one environmental condition and a manufacturing method capable of yielding such a device.